A mud motor or rotary steerable drilling tool may be used in directional drilling to control the curvature of a wellbore. The torque transmitted through a power section of the mud motor may drive a shaft of the mud motor having a drill bit at one end. Axial and lateral forces generated during a drilling operation of the mud motor may be resisted using a bearing assembly surrounding the driveshaft. The bearing assembly may include rotating components attached to the driveshaft.
A taper lock mechanism may be used to couple the bearings to the driveshaft. The taper lock mechanism may use a wedged insert to lock the axial and rotation movement of the rotating parts to the driveshaft. But, this mechanism may not be reliable during drilling operations as the axial loads generated during drilling may reach around 100,000 pounds. Similarly, a threaded connection may be used to mount the bearing assembly to the driveshaft. But, threads on the driveshaft may have several disadvantages, making them undesirable for mounting a bearing assembly to the driveshaft. For example, threadably coupling the bearings to the driveshaft may generate high stress concentrations to the driveshaft, increasing the likelihood of failure. Since the threads on the driveshaft may be prone to damage, they may require additional time and cost to extend the service life of the bearing assembly components and the driveshaft. In some instances, significant thread damage may require replacement of an expensive driveshaft. Further, threading on the driveshaft may require increased third-party inspection, which may result in lost time and money due to additional cleaning done prior to inspection and the downtime of the drilling operations during the inspections.